The present invention relates generally to fuel pumps for vehicles and, more particularly, to pressure equalization in a fuel pump of a vehicle.
It is known to provide a fuel tank in a vehicle to hold fuel to be used by an engine of the vehicle. It is also known to provide a fuel pump to pump fuel from the fuel tank to the engine. One type of fuel pump is known as a high-pressure turbine fuel pump. The high-pressure turbine fuel pump typically includes an impeller rotatable between inlet and outlet plates. The impeller is of a closed vane type to improve pump efficiency and performance. The impeller has a hub portion, a plurality of blade tips extending radially from the hub portion and disposed circumferentially thereabout and a peripheral ring portion extending radially from the blade tips. However, the closed vane impeller is hampered by flow loss due to wear of a peripheral ring portion that shrouds the blade tips of the impeller.
The peripheral ring that shrouds the blade tips of the closed vane impeller functions as an axial sealing surface between the fluid pressure within a flow channel and the fluid pressure surrounding a major diameter of the impeller. The pressure in an outside diameter cavity or gap formed between a major or outside diameter of the impeller and a spacer ring typically reaches equilibrium at a value equal to 50% of an outlet pressure of the fuel pump. The pressure within the flow channel can be approximated by a linear pressure gradient starting at a low pressure at an inlet port and increasing to pump outlet pressure at an outlet port. An analysis of the radial pressure differential across the peripheral ring portion of the impeller shows a leakage potential directed from the outside diameter cavity inward for the channel region of the flow channel between the inlet port and a channel length midpoint (xcex94P=0.5*outlet pressure channelxe2x88x92pressure at given channel location). Between the channel midpoint and the outlet port, the leakage potential is directed outward from the flow channel to an outside diameter cavity midpoint (xcex94P=channel pressure at given channel locationxe2x88x920.5*outlet pressure). Therefore, flow is leaking out of the last half of the flow channel and into the first half of the flow channel. The pressure differential across an axial seal surface of the peripheral ring portion of the impeller provides the potential for this leakage.
Therefore, it is desirable to minimize the flow loss associated with axial wear of the peripheral ring portion of the impeller while maintaining performance benefits the peripheral ring portion provides in a fuel pump for a vehicle. It is also desirable to provide pressure equalization of an impeller in a fuel pump for a fuel tank in a vehicle. It is further desirable to improve fuel pump durability using existing low cost materials and production feasible methods for a fuel pump for a fuel tank in a vehicle.
It is, therefore, one object of the present invention to provide pressure equalization of an impeller in a fuel pump for a fuel tank in a vehicle.
It is another object of the present invention to provide a fuel pump for a vehicle that minimizes flow loss associated with axial wear of a peripheral ring portion of an impeller.
To achieve the foregoing objects, the present invention is a fuel pump for a vehicle including a pump section having a flow channel and a rotatable impeller cooperating with said flow channel to pump fuel therethrough. The fuel pump also includes a motor section disposed adjacent the pump section and having a motor to rotate the impeller. The fuel pump further includes an outlet section disposed adjacent the motor section to allow pumped fuel to exit the fuel pump. The pump section includes a mechanism for minimizing leakage of fuel from the flow channel radially and equalizing pressure across a sealing surface of the impeller.
One advantage of the present invention is that pressure equalization of an impeller in a fuel pump is provided for a vehicle. Another advantage of the present invention is that the fuel pump uses existing low cost materials and production feasible methods. Yet another advantage of the present invention is that the fuel pump improves fuel pump durability due to increased axial clearance and less flow loss. Still another advantage of the present invention is that the fuel pump provides a mechanism to minimize flow loss associated with axial wear of a peripheral ring portion of an impeller while maintaining the performance benefits the peripheral ring portion provides.
Other objects, features and advantages of the present invention will be readily appreciated, as the same becomes better understood, after reading the subsequent description taken in conjunction with the accompanying drawings.